Examples of supports generally used for photographic light-sensitive materials include films or sheets of cellulose esters, synthetic polymers such as polystyrene, polycarbonate, and polyethylene terephthalate, glass, paper, and .alpha.-olefin-coated paper. At least one silver halide photographic emulsion layer is coated, directly or through a subbing layer, on the support. With many light-sensitive materials, to prevent them from being scratched or damaged when they come into contact with each other or with different light-sensitive materials, or during the processing thereof, a surface protective layer is coated on the photographic emulsion layer. In addition, other layers are coated of gelatin, other hydrophilic colloids, or vinyl polymer latexes, containing various additives such as dyes, antistatic agents, hardening agents, color-forming couplers, and anti-halation agents, for example, an anti-halation layer, an inter layer, a filter layer, and an antistatic layer.
Ordinary photographic light-sensitive materials typically comprise many hydrophilic organic colloid layers coated on the support. In the production of such light-sensitive materials, it is necessary that coating solutions forming the colloid layers be coated in a thin layer form, uniformly and at high speed, without causing any coating troubles such as repelling. In many cases, these coating solutions are coated at the same time; that is, simultaneous multi-layer coating is employed. For example, a color photographic light-sensitive material is produced by continuously coating photographic emulsion layers having different light-sensitive regions. Coating gelatin or colloid solutions onto a colloid layer of gelatin, while satisfying the necessary coating characteristics is, for example, more difficult than direct coating of gelatin or colloid solutions on the support. Such coating is particularly difficult when the colloid layer previously coated on the support is in the condition that it is cooled just after being coated.
In the production of color photographic light-sensitive materials, additives that are sparingly soluble in water, such as color couplers, ultraviolet absorbers, and brightening agents, are typically dissolved in high boiling organic solvents such as phthalates and phosphates, and thereafter dispersed or emulsified in hydrophilic organic colloids, particularly a gelatin solution in the presence of surface active agents, to prepare a coating composition for forming a hydrophilic organic colloid layer. In this case, if the amount of the surface active agent to be used as an emulsifying agent is too large, it becomes more difficult to coat another hydrophilic organic colloid layer on the earlier-prepared hydrophilic organic colloid layer. If, on the other hand, it is too small, the photographic light-sensitive material obtained has unstable photographic characteristics.
Various anionic surface active agents have been used as coating aids for coating solutions to be used in the production of photographic light-sensitive materials. Typical examples of such anionic surface active agents are described in U.S. Pat. Nos. 2,240,476, 3,026,202, 3,068,101, 3,220,847, 3,415,649, West German Pat. No. 1,942,665, etc.
These anionic surface active agents, however, have a disadvantage in that when added to a gelatin coating solution, they are readily precipitate as solid hydrates, thereby seriously reducing the coating properties of the gelatin coating solution, because the solubilities of the anionic surface active agents are significantly decreased by alkaline earth metal ions such as calcium contained in gelatin.
Japanese Patent Application (OPI) No. 98235/79 discloses that if alkaline earth metal salts of certain anionic surface active agents with ethylene oxide introduced thereinto are used, the resulting gelatin coating solution has good coating properties even if it contains alkaline earth metal ions such as calcium ions (the term "OPI" as used herein means a "published unexamined Japanese patent application"). The presence of the alkaline earth metal salts of anionic surface active agent reduces coating problems such as "repelling", and permit the production of a gelatin coating solution having somewhat better coating properties than those obtained using conventional anionic surface active agents. However, such coating solution fail to satisfy high speed-coating properties that have come to be required in the production of silver halide light-sensitive materials in recent years.